The principal objective of this research proposal is the determination of the three dimensional structure of protein molecules using x-ray diffraction analysis of their crystals, in particular the structure analysis of turkey egg white lysozyme and an intact human IgG immunoglobulin are being undertaken. The rotational and translational parameters relating the known structure of hen egg white lysozyme and the unknown structure of turkey egg white lysozyme have been determined by the method of rotation function and packing analysis respectively. An electron density map has been calculated at 2.8 A resolution and is being interpreted. The human IgG immunoglobulin crystals have been improved in their quality by growing the crystals in the presence of monomers of styrene before collecting the diffraction data. This has the effect of reducing the radiation damage and extending the diffraction data to a resolution of 4 A. Several heavy atom derivatives have been prepared for determining the phase angles of all the reflections. The heavy atom parameters are being refined before calculating the phase angles.